Note: The following methods are untested (by me) to ensure clear instruction for usage, and were obtained from the thread listed at the bottom. Testing is on my list of things to do. Others are welcome to do so, and submit an update.

Console
To disable tab completion and backspace beeping (anything else?), while allowing system beeps (such as emerge output), add the following to /etc/inputrc:

Code:

set bell-style none

- or -

Code:

set bell-style visual

To disable console beeping for the current console:

Code:

setterm -blength 0

To disable console beeping for another terminal than the one you are currently in (where <num> is the number of the terminal to disable beeping):